GS9077 Datasheet, PDF (8/14 Pages) Gennum Corporation – HD-LINX III SD-SDI Cable Driver

4. Detailed Description
GS9077 Data Sheet
4.1 Input Interfacing
DDI/DDI are high impedance differential inputs. The equivalent input circuit is shown
in Figure 3-1.
Several conditions must be observed when interfacing to these inputs:
• The differential input signal amplitude must be between 300 and 2200mVpp.
• The common mode voltage range must be as specified in the DC Electrical
Characteristics on page 4.
• For input trace lengths longer than approximately 1cm, the inputs should be
terminated as shown in the Typical Application Circuit.
The GS9077 inputs are self-biased, allowing for simple AC coupling to the device.
For serial digital video, a minimum capacitor value of 4.7µF should be used to allow
coupling of pathological test signals. A tantalum capacitor is recommended.
4.2 Output Interfacing
The GS9077 outputs are current mode, and will drive typically 800mV into a 75Ω
load. These outputs are protected from accidental static damage with internal ESD
protection diodes.
In order for a DDI output circuit using the GS9077 to meet this specification, the
output application circuit shown in Typical Application Circuit on page 10 is
recommended.
The value of L_COMP will vary depending on the PCB layout, with a typical value of
5.6nH. A 4.7µF capacitor is used for AC coupling the output of the device. This
value is chosen to ensure that pathological signals can be coupled without a
significant DC component occurring. Please see Application Information on
page 10 for more details.
44619 - 0 May 2007
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